DHAKA, Aug 5 (Reuters) - Bangladeshi rescuers struggled against a strong current and choppy river waters on Tuesday in the search for a ferry that capsized with more than 200 passengers on board, leaving about 120 missing, many of them feared dead.

Low-lying Bangladesh, with extensive inland waterways and slack safety standards, has an appalling record of ferry accidents, with casualties sometimes running into the hundreds.

Overcrowding is a common feature of many of the accidents, and each time the government vows to toughen regulations.

The ferry involved in Monday's incident, the MV Pinak-6, had a capacity to carry only 85 passengers, according to the country's inland transport authority, and sank in the river Padma about 30 km (18 miles) southwest of the capital, Dhaka.

"The navy rescue team started using sonar from this morning to locate the ferry," said Mohammad Saiful Hasan Badal, deputy commissioner of the Munshiganj district, where the ferry went down.

But a strong current and choppy waters were complicating the task, Saiful said, while the depth of the water and the thick sand encrusting the river bottom added to the difficulty.

"Due to the depth of the river and heavy sand the task has become more difficult," he added.

Teams from the country's military, coast guard, the Inland Water Transport Authority and the fire brigade had been pressed into the rescue effort, Saiful said.

About 100 passengers were rescued after the vessel sank, with two women taken to hospital dying on Monday. There was a possibility some of those aboard at the time had swum to the riverbank, Saiful told Reuters.

"Till now we have recorded 120 passengers as missing, but it does not mean that all of them are dead," he added.

Survivor Mohammad Suman told Reuters two of his brothers and a sister were missing.

"We were five all together, and I and my brother-in-law survived by jumping from the ferry," he said.

Most passengers aboard the ferry were returning to the city after celebrating Eid al-Fitr at the end of the holy fasting month of Ramadan, when many people in the predominantly Muslim nation return to their home villages to reunite with families.

In March 2012, a ferry sank near the same spot, killing at least 145 people. (Reporting by Serajul Quadir; Editing by Clarence Fernandez)